On Wed, 18 Nov 2009, Oliver Neukum wrote: > Am Mittwoch, 18. November 2009 11:41:25 schrieb Jiri Kosina: > > > User space receives the hotplug event for the class device, makes the > > > device node and notifies another program that opens the device node. > > > The program opens the device node which calls into usb_open and then > > > skel_open. skel_open calls usb_find_interface. usb_find_interfaces > > > searches the klist_devices of skel_driver, finds no device associated > > > with the minor number and returns NULL. skel_open returns -ENODEV. > > > > > > Control returns to really_probe and really_probe calls driver_bound > > > which adds the device to the list of devices associated with > > > skel_driver (klist_devices). > > > > > > I'm not sure what the right way to solve this is. A call to > > > wait_for_device_probe() in the skel_open call before calling > > > usb_find_interface fixes the problem, but it is a rather large hammer. > > > > Device core code is hard to follow, but I tried. > How about simply covering all of usb_register_dev() with minor_rwsem? That won't help. The window is between the end of usb_register_dev() and the end of skel_probe(), during which time the mutex isn't held. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
